Move trials link to be only an ee concern

What does this MR do and why?

• Move trials link to be only an ee concern
  • no need for this to be in foss as trials is purely a .com concern in ee
• change from trials registrations link(for non registered users) to trials new link since the link only exists for registered/signed in users

Screenshots or screen recordings

no change

old nav	new nav

How to set up and validate locally

see steps in !110683 (merged) for super sidebar

1. Setup to simulate SaaS and restart GDK
   • Make sure Admin > Settings > General > Sign Up Restrictions match the below (no admin approval, but hard email confirmation)
2. Under Admin -> General -> Account and Limit, enable Check feature availability on namespace plan
3. create a new group with a fresh/new user
4. wait 10 minutes or comment out the caching in https://gitlab.com/gitlab-org/gitlab/-/blob/855dc78c6793d2be3a0ba7693577525461f3fc16/ee/app/helpers/ee/users_helper.rb#L38-38
5. Observe dropdown for user on each nav experiences for link

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #404926